l.t.test_opensource : module documentation

XXX BarryWarsaw 14-May-2008: This shim is here so that the tests within the
launchpadlib and wadllib packages (living in the opensource directory) will
run as part of Launchpad's standard test suite. Those tests cannot yet be run
on their own, since they require a running Launchpad appserver, but not the
real Launchpad!. Eventually, there will be mock objects in the packages' test
suites so that they can be run on their own outside the Launchpad development
environment.